/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.accumulo.core.rpc;

import static java.util.Objects.requireNonNull;

import java.security.PrivilegedAction;

import org.apache.hadoop.security.UserGroupInformation;
import org.apache.thrift.transport.TTransport;
import org.apache.thrift.transport.TTransportException;
import org.apache.thrift.transport.TTransportFactory;

/**
 * A TransportFactory that wraps another one, but assumes a specified UGI before calling through.
 *
 * This is used on the server side to assume the server's Principal when accepting clients.
 *
 * Borrowed from Apache Hive 0.14
 */
public class UGIAssumingTransportFactory extends TTransportFactory {
  private final UserGroupInformation ugi;
  private final TTransportFactory wrapped;

  public UGIAssumingTransportFactory(TTransportFactory wrapped, UserGroupInformation ugi) {
    requireNonNull(wrapped);
    requireNonNull(ugi);

    this.wrapped = wrapped;
    this.ugi = ugi;
  }

  @Override
  public TTransport getTransport(final TTransport trans) {
    return ugi.doAs((PrivilegedAction<TTransport>) () -> {
      try {
        return wrapped.getTransport(trans);
      } catch (TTransportException e) {
        throw new RuntimeException(e);
      }
    });
  }
}
